Control drag on a rigid body (unity script)

drag.cs

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public Rigidbody rb;
    void Start() {
        rb = GetComponent<Rigidbody>();
    }
    void OpenParachute() {
        rb.drag = 20;
    }
    void Update() {
        if (Input.GetButton("Space"))
            OpenParachute();
        
    }
}